Method to determine the risk for side effects of an SSRI treatment in a person

ABSTRACT

A new method is found to determine an increased risk for side effects of an SSRI treatment in a person by genotyping the person for the presence of the 102 C/C DNA sequence in the 5-HT 2A  receptor gene. This provides for a method to improve the treatment of an SSRI responsive disorder and in particular depression.

FIELD OF THE INVENTION

The invention relates to a method to determine the risk for side effectsof an SSRI treatment in a person and to a method to improve medicaltreatment of a disorder, which is responsive to treatment with aselective serotonin reuptake inhibitor (SSRI).

BACKGROUND OF THE INVENTION

SSRI's are widely used for the treatment of various disorders. Majordepression is the most common among those disorders treated with anSSRI. Other well-known disorders that can be treated with SSRI's aredysthymia, premenstrual dysphoric disorder, panic disorder, obsessivecompulsive disorder, social phobia, post-traumatic stress disorder,generalised anxiety disorder, obesity and alcoholism (Schatzberg J. ClinPsychiatry, 61, Suppl 11: 9-17, 2000; Masand and Gupta, Harvard RevPsychiatry, 7: 69-84, 1999). Evidence is accumulating that such drugshave also beneficial effects in less common disorders, such astrichotillomania, paraphilia and related disorders and borderlinepersonality disorder. Benefits are also obtained with use of an SSRI insmoking cessation and in the control of addictive behavior.

It occurs regularly that a once started treatment with an SSRI fails tohave clear therapeutic results or has to be discontinued due to poortolerance of side effects. Known side effects of SSRI's are headache,nausea, appetite inhibition, agitation, sleep disturbance, anddisturbance of sexual functions, such as anorgasmia and loss of libido.In practice the overall therapeutic result of a regularly applied SSRItreatment is the resultant of the improvement of the disorder and theburden of negative side effects. In view of the existence ofalternatives to SSRI's for the treatment of disorders, treatment resultscan be improved when patients are selected for tolerance and chance ofsuccess of an SSRI. Patients at risk for negative side effects can betreated with a treatment other than a treatment with an SSRI.Consequently, it will be very useful if it were possible to predict theoccurrence of cumbersome side effects of a treatment with an SSRI.

It is a known assumption that the genetic make-up of a person cancontribute to the individually different responses of persons to amedicine (Roses, Nature 405:857-865, 2000). Examples of genetic factors,which determine drug tolerance, are drug allergies and severely reducedmetabolism due to genetic absence of suitable enzymes. A case of alethal lack of metabolism due to cytochrome P-450 2D6 genetic deficiencyis reported by Sallee et al J Child & Adolesc. Psychopharmacol, 10:27-34, 2000. The metabolic enzymes in the liver occur in polymorphicvariants, causing some persons to metabolise certain drugs slowly andmaking them at risk for side effects due to excessively high plasma druglevels. Many genes that are expressed in the brain such asneurotransmitter receptors and transporter proteins have polymorphicvariants. These variants may influence the interaction of a drug withcells of the brain, which may influence the frequency of drug sideeffects (Cravchik and Goldman, Arch Gen Psychiatry 57:1105-1114, 2000).Variants of the gene for the serotonin 2A receptor (5-HT_(2A) receptor)exist, which differ in one nucleotide at location 102. Alleles with 102Cand 102T exist. This particular polymorphism has been explored inattempts to find genetic predictors for schizophrenia symptomatology,suicidal ideation, alcohol dependency, bipolar affective disorder,fibromyalgia, Tourette's syndrome, and other diseases. Such attemptshave met with little confirmed success thus far (Bondy et al., Am J MedGenetics, 96:831-835, 2000; Massat et al., Am J Med Genetics,96:136-140, 2000; Serretti et al., Am J Med Genetics, 96: 84-87, 2000;Bondy et al., Neurobiol Diseases, 6:433-439, 1999; Du et al., Am J MedGenetics, 96:56-60, 2000).

SUMMARY OF THE INVENTION

Unexpectedly, it has now been found that it is possible to determine anincreased risk for side effects of an SSRI treatment in a person bygenotyping the person for the presence of the 102 C/C DNA sequence inthe 5-HT_(2A) receptor gene.

This finding also enables that an improved treatment result for adisorder which is responsive to treatment with an SSRI, can be obtainedby genotyping the patients for the presence or absence of said DNAsequence and selecting a therapy which diminishes the risk for sideeffects of an SSRI treatment.

In particular, the improvement is obtained in the treatment ofdepression for which it is preferred to select as therapy administeringmirtazapine in an amount effective to treat depression in the personhaving the 102 C/C DNA sequence in the 5-HT_(2A) receptor gene.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Genotyping a person for the presence of the 102 C/C DNA sequence in the5-HT_(2A) receptor gene means screening patients to determine the typeand number of 5-HT_(2A) receptor alleles present in the patient. Suchscreening may be carried out by nucleic acid sequencing of DNA. Forexample, the screening may be accomplished by restriction isotypingmethods, which include the general steps of polymerase chain reactionamplification, restriction digestion, and gel electrophoresis. Screeningmay also be carried out by other types of nucleic acid sequencing, e.g.,by hybridisation or oligotyping, or by direct sequencing of DNAnucleotides.

5-HT_(2A) receptor gene means the gene (designated as HTR2A) whichencodes for the serotonin 5-HT_(2A) receptor. The 5-HT_(2A) receptorgene is located on chromosome 13q14-21. At location 102 a C→Tpolymorphism is known with about 40% frequency of the 102T allele in anormal Caucasian population. The terms allele and gene are usedinterchangeably herein. The DNA and amino acid sequences of the5-HT_(2A) receptor gene and the 5-HT_(2A) receptor itself are known andare available, e.g., at NCBI nucleotide accession No. NM_(—)000621 andprotein accession No. NP_(—)000612.

The term 102 C/C DNA sequence refers to homozygous presence of cytidineat location 102 in both alleles for the 5-HT_(2A)-receptor. The terms102 T/C and 102 T/T refer to the heterozygous state, and the homozygousstate for thymidine at location 102 of the 5-HT_(2A)-receptor,respectively. The homozygous C/C genotype occurs with a frequency ofabout 33% in Caucasian populations (Frisch, Mol Psychiatry 4:389-392,1999).

Side effects of an SSRI treatment are those related to SSRI treatmentbased on a positive correlation between frequency or intensity ofoccurrence and SSRI drug treatment. Such information is usuallycollected in the course of studies on efficacy of a drug treatment andmany methods are available to obtain such data. Resulting information iswidely distributed among the medical profession and patients receivingtreatment. Specifically identified SSRI treatment related side effectsare headache, dizziness, agitation, trouble concentrating,gastrointestinal disturbances, nausea, vomiting, diarrhea, appetiteinhibition, sleep disturbance, somnolence, insomnia and disturbance ofsexual functions, such as anorgasmia and loss of libido. Prematuredrug-related discontinuation of an SSRI treatment and drug-relatedadverse events are also included here within the definition of sideeffects of an SSRI treatment.

A treatment result is defined here from the point of view of thetreating doctor, who judges the efficacy of a treatment as a groupresult. Within the group, individual patients can recover completely andsome may even worsen, due to statistical variations in the course of thedisease and the patient population. Some patients may discontinuetreatment due to side effects, in which case no improvement in theircondition due to SSRI treatment can occur. An improved treatment resultis an overall improvement assessed over the whole group. Improvement canbe solely due to an overall reduction in frequency or intensity of sideeffects. It is also possible that doses can be increased or the dosingregime can be stepped up faster thanks to less troublesome side effectsin the group and consequently an earlier onset of recovery or betterremission of the disease.

A disorder, which is responsive to treatment with an SSRI, is defined tobe a disorder, which is, according to recommendations in professionalliterature and drug formularies, known to respond with at least partialremission of the symptoms to a treatment with an SSRI. In most countriessuch recommendations are subject to governmental regulations, allowingand restricting the mention of medical indications in package inserts.Other sources are drug formularies of health management organisations.Before approval by governmental agencies certain recommendations canalso be recognised by publications of confirmed treatment results inpeer reviewed medical journals. Such collective body of informationdefines what is understood here to be a disorder which is responsive totreatment with an SSRI. Being responsive to SSRI treatment does notexclude that the disorder in an individual patient can resist treatmentwith an SSRI, as long as a substantial portion of persons having thedisorder respond with improvement to the SSRI treatment.

In the section describing the background of the invention examples ofSSRI responsive disorders were listed. Known disorders which areresponsive to treatment with an SSRI are, for example, major depressivedisorder, dysthymia, premenstrual dysphoric disorder, panic disorder,obsessive compulsive disorder, social phobia, post-traumatic stressdisorder, generalised anxiety disorder, obesity, bulimia nervosa,alcoholism, trichotillomania, paraphilia and related disorders,borderline personality disorder, smoking cessation and drug abuse.

The technical field defines an SSRI as a drug which inhibits thereuptake of serotonin in nerve terminals in the brain more effectivelythan the reuptake of noradrenaline and dopamine. Such drugs are treatedas a group with common properties due to this mechanism of action andthis selectivity. Known drugs specifically named as SSRI are fluoxetine,fluvoxamine, citalopram, cericlamine, femoxetine, sertraline,paroxetine, ifoxetine, cyanodothiepin and litoxetine, of whichfluoxetine, fluvoxamine, citalopram, sertraline and paroxetine are theones with which most experience is obtained and which are preferredindicators for defining the SSRI responsive disorders for which themethod according to this invention can be applied (Hermann, Canadian JClin Pharmacol 7: 91-95, 2000; Modell et al., Clin Pharm & Ther 61:476-487, 1997; Lucki et al., Neurosci biobehav. Rev 18: 85-95, 1994).

The method to obtain an improved treatment result comprises:

-   -   a) Diagnosing a person for having a disorder, which responds to        treatment with an SSRI.    -   b) Genotyping the person to determine whether the person is a        homozygous carrier of 102C alleles of the gene for the        5-HT_(2A)-receptor.    -   c) Adapt the further treatment of the person differentially        depending on the presence or absence of the said sequence in the        person.

This method does not necessarily prescribe these steps in the indicatedsequence. In practice an SSRI treatment can be started before the stepsto confirm the suitability of the treatment can be started. Thegenotyping serves to decide on timely adapting the further treatmentwhen the person is found to fall into the genotype category homozygous102 C/C for the 5-HT_(2A) receptor.

For further treatment the category (A) of persons of the homozygous 102C/C genotype is to be differentiated from the category (B) of persons ofthe 102 T/C and T/T genotypes.

Adapting the further treatment of the person differentially depending onthe presence or absence of the said sequence in the person is a measurewhich should consist of the following measures:

For category A the further treatment should be either

-   -   1) administering a below average dose of an SSRI, or    -   2) co-administering a drug treatment which diminishes SSRI side        effects, or    -   3) instructing and helping the person to accept the        inconveniences of the side effects, or    -   4) starting or switching to an alternative, non-SSRI treatment.

For category B the further treatment should be either

-   -   1) starting or continuing as if no information on said genotype        is available    -   2) a more aggressive approach in the treatment with an SSRI, in        the case that an SSRI-treatment is or is to be selected, by        administering the person a higher dose or stepping up the dose        in a more progressive regime than would be done if no        information on the genotype was known.

The adaptation for category A persons amounts to selecting a therapydiminishing the risk for side effects of an SSRI treatment for theperson. Preferred is to apply a therapy which is recognised to be analternative for a treatment with an SSRI.

When the genotyping is performed, or the result is known, after start ofan SSRI treatment and the treated person is found to have the 102 C/Cgenotype and side effects are experienced with SSRI treatment, then,because there is a high probability that the person will eventuallydiscontinue SSRI treatment, the person's burden can be decreased byapplying an alternative treatment. As a result the time required toachieve an improvement can be reduced by applying an alternativetherapy, since the probability of eventually discontinuing treatmentwith the SSRI is high in a person with the 102 C/C genotype.

The selection of a therapy which is recognised to be an alternative fora treatment with an SSRI is defined by reference to the generalknowledge in this medical field. It is standard practise to diagnose adisorder in a person and select a therapy which is indicated for thedisorder. An example of a reference manual for diagnostic methods is theDiagnostic and Statistical Manual of Mental Disorders 4th edition(DSM-IV) published by the American Psychiatric Association, Washington,D.C. (1994). Supplementary to this the SSRI responsive disorders can beidentified objectively on the basis of recommendations in governmentapproved labels, by health management organisations and in confirmedreports of positive treatment results in peer reviewed medicalliterature, it is similarly known to the skilled person that alternativenon-SSRI treatments are available. Examples of non-SSRI antidepressanttreatments are, for example, treatments with drugs, which act byblocking the reuptake of norepinephrine, or by blocking α₂ adrenergic orserotonin receptors. Specific alternative antidepressants arevenlafaxine, mirtazapine, nefazodone, doxepine and imipramine, of whichmirtazapine, of course in an amount effective to treat depression, ispreferred for the indication of major depression. Alternative treatmentsfor prescribing an SSRI can also be non-drug treatments, such asbehavioural therapies or electroconvulsive shock treatment.Benzodiazepine-like anxiolytic compounds can be used for anxietydisorders. A therapy diminishing the risk for side effects of an SSRItreatment can also be a treatment with a below average dose of the SSRIor providing an additional treatment to prevent side effects.

The amount of mirtazapine effective to treat depression will, of course,vary and is ultimately at the discretion of the medical practitioner.The factors to be considered include the route of administration andnature of the formulation, the body weight, age, and general state ofhealth, and severity of the depression. Unless otherwise stated, allweights of active ingredients referred to herein are calculated in termsof the active drug per se. In general, a suitable dose of mirtazapinefor administration to a human will be in the range of 5 to 100 mg perday. In one embodiment, the suitable dosage range for administration ofmirtazapine to a human may be 15 to 45 mg per day. The desired dose maybe presented as two, three, four, five, or more sub-doses administeredat appropriate intervals throughout the day. These sub-doses may beadministered in unit dosage forms, for example, containing 15 mg, 30 mg,or 45 mg, or any unit dosage useful to allow multiple dosing in a singleday.

No clear explanation of the effect of the invented method can be given.It may be relevant that the 5-HT_(2A) receptor is located on themembrane of postsynaptic neurones and interacts with serotonin moleculesin the synaptic cleft. It has been theorised that the side effects ofselective serotonin reuptake inhibitors such as paroxetine are mediatedthrough this receptor. Genetic variants of the 5-HT_(2A) receptor mayalter the binding of serotonin to the receptor, or alter the signal thatthe activated receptor transmits to the postsynaptic neuron in thebrain. 5-HT_(2A) receptors are also located on smooth muscle cells inthe gastrointestinal tract and blood vessels. Carriers of the C/Cgenotype may have side effects such as gastrointestinal upset anddizziness after paroxetine due to altered reaction of smooth musclecells to serotonin stimulation of 5-HT_(2A) receptors. 5-HT_(2A)receptors are also thought to be important in level of alertness andsleep. Insomnia and agitation experienced by subjects carrying the C/Cgenotype may have been due to altered function of 5-HT_(2A) receptorsregulating alertness and sleep.

The 5-HT_(2A) receptor 102 T/C polymorphism is a “silent” genetic markerthat does not result in an amino acid substitution in the functionalprotein. Without implying any restriction on the claims and use of theinvention it can be suggested that the effect we have found onintolerance to an SSRI of 102C/C genotype patients can be due to anothernearby variant in the gene that directly affects its function. The 102T/C polymorphism and the functional variant are said to be in “linkagedisequilibrium”, meaning that the 102 T/C variant is a marker for apolymorphism in close proximity that affects the receptor function.However, this in no way diminishes the importance of the 102 T/Cpolymorphism as a predictor of side effects to an SSRI, as found in thepresent invention. Many existing medical tests are useful markers for anunderlying biological process. For example, the erythrocytesedimentation rate (ESR) is a commonly used marker for an inflammatoryreaction, even though it does not define the exact nature of theunderlying inflammatory disease.

To screen patients for the gene, genomic DNA can be extracted fromEDTA-treated whole blood using, for example, the Puregene DNA extractionkit (available from Gentra Systems). Genotypes can be determined usingrestriction isotyping (restriction enzyme isoform genotyping) followingin general the method of Du et al. (Am J Med Genet. Feb. 7,2000;96(1):56-60). Thus, the 5-HT_(2A) gene presence in the extract canbe amplified by about 30 cycles of polymerase chain reaction primed bythe primers 5-HT2AR-1 (agcagaaactataacctgtt) and 5-HT2AR-2(caagtgacatcaggaaatag) followed by a final extension step. This PCRproduct can be digested with a specific restriction enzyme cutting5-HT2A polynucleotides as a consequence of recognition of the 102 C/Tdifference such that one allele remains undigested, yielding the full410 base pair fragment, while the other allele is cut into twofragments. The digested samples can then be separated and determined bygel electrophoresis.

EXAMPLE

Treatment Protocol

122 patients with major depression were treated for 8 weeks withparoxetine. All subjects were 65 years of age or older and had been freeof major medical problems for at least 3 months. At screening, all metDSM-IV criteria for major depression (single or recurrent), had MiniMental State Examination scores above the 25th percentile for their age,and had a Hamilton Depression Rating Scale 17-item (HDRS-17) score of atleast 18. Patients were excluded for clinically significant laboratoryabnormalities, drug or alcohol abuse, psychosis, recent suicide attempt,and psychiatric conditions other than major depression, or treatmentwith antidepressant medications within 7 days of commencing the study.

Initial treatment was with 20 mg of paroxetine (two 10 mg capsules)given each evening. On day 14, doses were increased to 30 mg ofparoxetine once daily. At days 28 and 42, dose increases to 40 mg ofparoxetine were allowed if the patient had a Clinical Global Impression(CGI) improvement score of greater than 2. Patients were seen in clinicat days 7, 14, 21, 28, 42, and 56 of treatment.

Genetic Analysis

Genomic DNA was extracted from EDTA-treated whole blood using thePuregene DNA extraction kit (Gentra Systems). Genotype for the 102 T/CDNA sequence polymorphism in the 5-HT_(2A) receptor gene was determinedusing the method of Du et al. (Am J Med Genet. Feb. 7,2000;96(1):56-60). Specifically, 2.5 μL 10× PCR buffer (AppliedBiosystems); 0.25 μL of 10 mmol/L dNTP (Amersham); 0.05 μL of primer5-HT2AR-1 (agcagaaactataacctgtt) at 100 pmol/μL; 0.05 μL of primer5-HT2AR-2 (caagtgacatcaggaaatag) at 100 pmol/μL; and 0.1 μL of Taqpolymerase at 5 U/μL (Applied Biosystems) are mixed with 1 μL of genomicDNA at 0.23 to 1.1 μg/μL in a total volume of 25 μL. After an initial 5minute denaturing step at 95° C., the reaction mixture goes through 30cycles of polymerase chain reaction (PCR) (95° C. for 1 min, 52° C. for30 sec, and 72° C. for 1 min), followed by final extension at 72° C. for10 minutes. 8 μL of this PCR product is digested with 0.5 μL of the MspI restriction enzyme (20 U/μL, NEB), 1.5 μL of 10× buffer 2, and 5 μL ofwater for 4 hours at 37° C. The digested samples are then separated on a2% agarose gel in a field of 4 V/cm. The T allele remains undigested,yielding the full 410 base pair fragment, while the C allele is cut into162 and 248 bp fragments.

Outcome Measures

Discontinuations were classified as due to any event, and as due to anadverse event. Severity of adverse events were obtained by clinicianratings that were standardised for drug exposure time and dosage. Plasmadrug levels were obtained at day 28. Body weight was determined atbaseline and at each subsequent visit. Actual medication taken wasdetermined by counting the number of tablets remaining at each clinicvisit. Dosing compliance was determined by as total number of medicationdoses taken divided by total number of capsules given.

Results

I. Genotypes Divided Two Ways (C/C Versus T/C and T/T Groups)

All Subjects

The frequencies of genotypes were:

-   -   Paroxetine C/C=41 patients (33.6%)    -   Paroxetine T carriers (T/C and T/T)=81 patients (66.4%)

Over the 8 week study, paroxetine C/C patients had:

-   -   Greater severity of adverse events due to study drug (p=0.03)    -   Lower final daily dose (p=0.08)    -   Lower dosing compliance (p=0.06)    -   Lower plasma levels at day 28 (p=0.056)    -   More subjects discontinuing early (p=0.049), and more subjects        discontinuing early due to adverse events (46.3% for C/C        genotype, 16% for other subjects; p=0.001)

(p values above are from F tests comparing mean values, or fromCochran-Mantel-Haenszel statistics comparing proportions. These valuesindicate statistically significant (p<0.05), or marginally statisticallysignificant (p<0.10) differences).

The lower final daily dose, lower dosing compliance, and lower plasmalevels were likely due to more severe side effects in patients with C/Cgenotype, resulting in decreased ability to take doses of paroxetinethat were well tolerated by other patients with the T/C and T/Tgenotypes.

Survival analyses for dropouts showed that patients with C/C genotypehad significantly greater likelihood of dropping out of the study thandid other subjects at every assessment point. Statistics below are pvalues from Kaplan-Meier survival analyses. That is, at day 7 theprobability that the increased dropout rate of patients with the C/Cgenotype was due to random factors was only 0.001, or one inone-thousand. This indicates that these results are highly reliable. Allcauses Adverse events Day 7 .003 .001 Day 14 .005 .001 Day 21 .009 .001Day 28 .009 .001 Day 42 .014 .001 Day 49 .008 .001

Caucasian Subjects

There were no significant differences between the two genotype groups inthe frequency of ethnic minorities. However, because of possible effectsof genetic background, data for Caucasians were analysed separately.

-   -   Paroxetine C/C=36 patients (33.0%)    -   Paroxetine T carriers (T/C and T/T)=73 patients (67.0%)

There were no significant differences between C/C and T/-groups in age,gender, ethnicity, baseline body weight, cognition, or severity ofdepression at baseline.

Paroxetine C/C subjects had:

-   -   Greater severity of side effects due to study drug (p=0.051)    -   More discontinuations due to any cause (C/C=63.9%; T/T and        T/C=45.2%) p=0.068    -   More discontinuations due to adverse events (C/C=47.2%; T/T and        T/C=16.4%) p<0.001

Survival Analyses showed C/C subjects had a significantly greaterprobability of discontinuation: All causes Adverse events Day 7 .006.001 Day 14 .010 .001 Day 21 .019 .002 Day 28 .019 .002 Day 42 .028 .004Day 49 .016 .001

I. Genotypes Divided Three Ways (C/C Versus T/C Versus T/T)

All Subjects

The data were also analysed with subjects divided into three genotypegroups.

-   -   41 subjects with C/C genotype (33.6%)    -   63 subjects with C/T genotype (51.6%)    -   18 subjects with T/T genotype (14.8%)    -   122 total

No significant differences were found between genotype groups in age,gender, ethnic origin, or body weight for either drug. No significantdifferences were found among genotype groups in final daily doseachieved, dosing compliance, plasma drug concentrations at day 28. Therewere no differences in average daily dose at each visit, except at day7, when C/C carriers took less medication than the other two genotypegroups. This was probably due to intolerance of the medication in C/Ccarriers.

The probability of discontinuation due to an adverse event was linearlyrelated to increasing dosage of the C allele (C/C=3, C/T=2, T/T=1). Thatis, the greater the number of C alleles, the higher the probability ofdiscontinuation. All causes Adverse event Day 7: NS .016 Day 14: .048.010 Day 21: .047 .009 Day 28: .047 .009 Day 42: NS .020 Day 49: .052.009(NS = no significant difference)

Caucasian Subjects, 3-Way Classification

-   -   36 subjects with C/C genotype (33.0%)    -   56 subjects with C/T genotype (56.0%)    -   17 subjects with T/T genotype (15.6%)

There were no significant differences among the 3 genotype groups (C/Cvs. T/C vs. T/T) in the frequency of ethnic minorities. However, becauseof possible effects of genetic background, data for Caucasians wereanalysed separately.

Among Caucasian subjects, there were no significant differences amongthe genotype groups in age, gender, body weight, final daily dose, oroverall dosing compliance.

At day 7, subjects with the C/C genotype took significantly lessparoxetine than subjects with C/T and T/T genotypes (p<0.035).

Survival analyses did not show a difference among the 3 genotype groupsin discontinuations due to any cause. However, discontinuations due toadverse events showed:

-   -   Day 7: 0.039    -   Day 14: 0.022    -   Day 21: 0.019    -   Day 28: 0.019    -   Day 42: 0.051    -   Day 49: 0.020

Results for Mirtazapine

122 additional patients with similar characteristics to those treatedwith paroxetine received mirtazapine treatment under the sameconditions. Initial treatment was with 15 mg mirtazapine (one activecapsule and one placebo capsule) given each evening. On day 14, doseswere increased to 30 mg once daily. At days 28 and 42, dose increases to45 mg of mirtazapine were allowed if the patient had a Clinical GlobalImpression (CGI) improvement score of greater than 2. All patients weregenotype for the 102 T/C polymorphism using the method described above.Results showed that mirtazapine-treated patients with the C/C genotypehad no greater probability of discontinuing treatment due to sideeffects than did other subjects, and no greater severity of side effectsthan others. These results are in marked contrast to those obtained withparoxetine treatment. Mirtazapine treated subjects also showedstatistically significant improvement in mood (decreased depression) asmeasured by the Hamilton Depression Rating Scale over the 8 weektreatment period. This result was not affected by the 102 T/Cpolymorphism.

Conclusion

These results illustrate the major effect of the 5-HT_(2A) receptor 102T/C polymorphism on adverse events in patients treated with paroxetine.Subjects of the C/C genotype had a significantly higher probability ofdiscontinuation due to adverse events than did other subjects at everyevaluation point during the 8 week study. Subjects of the C/C genotypealso took significantly less medication taken at day 7, and showedtrends toward a lower final daily dose, and lower dosing compliance.This suggests that the subjects with C/C found paroxetine unpleasant dueto side effects. The side effects experienced by subjects with the C/Cgenotype were more severe than those experienced by other subjects.Typical side effects experienced by C/C carriers who dropped out of thestudy included dizziness, somnolence, insomnia, agitation, troubleconcentrating, vomiting, nausea, and diarrhea.

The association between the 102 T/C polymorphism and discontinuationsdue to adverse events is present in both the full sample as well as inthe subsample of Caucasian subjects. This indicates that the result isnot due to population stratification, meaning the result is not due toincluding subjects of different ethnic backgrounds in the study. Theresult is robust regardless of whether the data are analysed as C/Cgenotype vs. T/C and T/T or with three genotype levels (C/C, T/C, T/T).

The comparison study with mirtazapine showed that the 102 T/Cpolymorphism does not affect severity of side effects or dropouts due toside effects in depressed patients treated with this medication.Patients treated with mirtazapine, including those with C/C genotype,showed a statistically significant improvement in mood at the end of the8 week study. This indicates that therapy with mirtazapine is aneffective and safe alternative to SSRI treatment in patients who havethe C/C genotype.

1. A method for determining an increased risk for side effects ofselective serotonin reuptake inhibitor (SSRI) treatment in a subject,comprising genotyping the subject for the presence of the 102 C/C DNAsequence in the subject's 5-HT_(2A) receptor gene.
 2. The methodaccording to claim 1, wherein the subject suffers from depression.
 3. Amethod to improve a treatment of an SSRI responsive disorder in asubject, comprising genotyping the subject for the presence or absenceof the 102 C/C DNA sequence in the subject's 5-HT_(2A) receptor gene andadapting the further treatment differentially depending on the presenceor absence of the said sequence in the subject.
 4. The method accordingto claim 3, wherein the 102 C/C DNA sequence is found in the subject's5-HT_(2A) receptor gene and the subject is treated with a psychoactivepharmaceutical composition free of selective serotonin reuptakeinhibitors.
 5. The method according to claim 4, wherein the SSRIresponsive disorder is depression and the further treatment is adaptedby administering mirtazapine in an amount effective to treat depression.